The testing for biocompatibility of newly developed dental and medical devices is an essential preclinical requirement. Controlled clinical studies represent the final test prior to marketing of any material. The Biological/Clinical Core will provide support services to evaluate the safety and efficacy of material developed by the Center. It will assist in the design and conduct biocompatibility analyses of candidate materials. Furthermore, it will take part in the design and performance of the clinical trials. The biological assays will include four cell culture techniques, subcutaneous implantations tests for toxicity assessments, and the pulp and dentin usage test. The results obtained in the studies will be presented in collaboration with the scientists involved in the development of new materials for the replacement of amalgam, and with the Biostatistical Core. The clinical studies will, for budgetary reasons, be limited to small, short term feasibility studies. Established direct (USPHS criteria) and indirect (replicas/impressions and photography) clinical techniques will be used to evaluate the results. The clinical feasibility studies will include resin-based composites retained by the new adhesive/bonding technique developed by the Center as well as the new composite with minimal shrinkage during polymerization. Inlays for the treatment of primary caries and for replacement of failed amalgam restorations will be inserted using the luting cements and the ceramic materials developed by the Center. Shell crowns, partial and full, will be used to restore extensively broken-down teeth. These restorations will not follow established principles for crown preparations. The shell crowns require maintenance of maximum amounts of enamel. Thus, they conserve whatever tooth structure is left. The small, short term clinical trials do not lend themselves to detailed statistical analyses, but they are feasibility studies in the true sense of the term and will form the basis for future R01 Grant Applications.